feat(web,store,latest): forced poll — Check now stamps a Series for the next Lane pass (#146)

The control writes series.force_poll_at (column landed in migration 0014)
and never commands the poller: pending is derived as force_poll_at >
latest_checked_at and self-clears because the check stamp is written before
the fetch. The due query's forced flag overrides the rest cutoff, the
Sighting-deferral and finished-only clauses, jumps the queue, and wakes a
sleeping browser Lane; it never overrides an empty series_url, the Bookmarks
join, the refusal backoff, the sidecar-down skip or the Lane gap.

ADRs: 0013-commands-through-the-database.

backend/internal/store/admin.go

@@ -41,7 +41,7 @@ type SeriesFilter struct {
 // must never leave the store package — so the projection does not select it,
 // and only the anonymous boolean in raisedByReaderAnswer crosses it.
 const adminSeriesColumns = `s.site, s.series_id, s.title, s.series_url, s.cover_address,
-	s.kind, s.latest_chapter, s.latest_chapter_num, s.latest_checked_at`
+	s.kind, s.latest_chapter, s.latest_chapter_num, s.latest_checked_at, s.force_poll_at`
 
 // raisedByReaderAnswer answers "did a Reader's report set this number" without
 // naming which Reader. Kept apart from adminSeriesColumns so the column list —
@@ -68,8 +68,12 @@ type AdminSeries struct {
 	LatestChapter    string
 	LatestChapterNum *float64 // nil until first captured
 	LatestCheckedAt  int64
-	ReaderCount      int
-	RaisedByReader   bool // a Reader's report set LatestChapterNum
+	// ForcePollAt is the owner's "check now" request stamp (issue #146), zero
+	// meaning never asked. Pending is derived, never stored: a request is
+	// pending while ForcePollAt is newer than LatestCheckedAt.
+	ForcePollAt    int64
+	ReaderCount    int
+	RaisedByReader bool // a Reader's report set LatestChapterNum
 }
 
 // SeriesPage is one page of the owner's filtered Series list plus the count
@@ -185,7 +189,7 @@ func (s *Store) SeriesPage(f SeriesFilter) (SeriesPage, error) {
 		`+where+`
 		GROUP BY s.site, s.series_id, s.title, s.series_url, s.cover_address,
 		         s.kind, s.latest_chapter, s.latest_chapter_num, s.latest_checked_at,
-		         s.latest_raised_by
+		         s.force_poll_at, s.latest_raised_by
 		`+having+`
 		ORDER BY s.latest_checked_at, s.site, s.series_id
 		LIMIT $`+strconv.Itoa(base+1)+` OFFSET $`+strconv.Itoa(base+2), args...)
@@ -260,6 +264,7 @@ func scanAdminSeries(scan func(...any) error) (AdminSeries, int, error) {
 	if err := scan(
 		&a.Site, &a.SeriesID, &a.Title, &a.SeriesURL, &a.CoverAddress,
 		&a.Kind, &a.LatestChapter, &latestChapterNum, &a.LatestCheckedAt,
+		&a.ForcePollAt,
 		&a.RaisedByReader, &a.ReaderCount, &total,
 	); err != nil {
 		return AdminSeries{}, 0, err